U.S. patent application number 15/567557 was filed with the patent office on 2018-04-26 for molding tool.
The applicant listed for this patent is OVERATH GMBH. Invention is credited to Eberhard LANG, Udo OVERATH.
Application Number | 20180111294 15/567557 |
Document ID | / |
Family ID | 53039272 |
Filed Date | 2018-04-26 |
United States Patent
Application |
20180111294 |
Kind Code |
A1 |
LANG; Eberhard ; et
al. |
April 26, 2018 |
MOLDING TOOL
Abstract
A molding tool for producing molded parts from expandable
plastic beads. The molding tool has an inner wall facing the molded
part and an outer wall facing away from the molded part, between
which a hollow space is formed for conveying a heating/cooling
medium, and the inner and outer walls are connected to each other
in some areas by spacers. Inside the spacers, through bores are
formed, which convey steam, pass through the outer and inner walls,
and are sealed relative to the hollow space.
Inventors: |
LANG; Eberhard; (Heilbronn,
DE) ; OVERATH; Udo; (Lohmar, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OVERATH GMBH |
D-53797 LOHMAR |
|
DE |
|
|
Family ID: |
53039272 |
Appl. No.: |
15/567557 |
Filed: |
April 25, 2016 |
PCT Filed: |
April 25, 2016 |
PCT NO: |
PCT/EP2016/059139 |
371 Date: |
October 18, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C 33/046 20130101;
B29K 2905/00 20130101; B29C 44/58 20130101; B29K 2105/048 20130101;
B29C 44/3434 20130101; B29C 33/04 20130101 |
International
Class: |
B29C 44/34 20060101
B29C044/34; B29C 44/58 20060101 B29C044/58 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 27, 2015 |
EP |
15165259.1 |
Claims
1. A molding tool (1) for producing molded parts from expandable
plastic beads, the molding tool (1) having an inner wall (10)
facing the molded part and an outer wall (12) facing away from the
molded part between which a hollow space (11) is formed for
conveying a heating/cooling medium (K), the inner and outer walls
(10, 12) are connected to each other in areas by spacers (13),
inside the spacers (13) through bores (130) are formed and convey
steam, pass through the outer and inner walls (10, 12), and are
sealed relative to the hollow space (11).
2. The molding tool (1) according to claim 1, wherein the spacers
(13) are positioned at regular intervals from one another in the
form of a grid.
3. The molding tool (1) according to claim 2, wherein the spacers
(13) function as flow dividers for the heating/cooling medium (K)
that can be conveyed through the hollow space (11).
4. The molding tool (1) according to claim 3, wherein the inner and
outer walls (10, 12) are oriented approximately parallel to each
other and spaced a constant distance apart from each other and the
spacers (13) extend perpendicular to the inner and outer walls (10,
12).
5. The molding tool (1) according to claim 4, wherein between
adjacent spacers (13) and the surfaces of the inner and outer walls
(10, 12) facing the hollow space (11), circular through flow
openings (14) are provided for the heating and cooling medium
(K).
6. The molding tool (1) according to claim 5, wherein the through
bores (130) inside the spacers (13) taper conically starting from
the outer wall (12) in a direction of the inner wall (10).
7. The molding tool (1) according to claim 6, wherein the through
bores (130) inside the spacers (13) conically taper from a starting
diameter of approximately 1.5 to 2 mm down to 0.3 to 0.5 mm.
8. The molding tool (1) according to claim 7, wherein the inner and
outer walls (10, 12) each have has a wall thickness of 0.3 to 3
mm.
9. The molding tool (1) according to claim 8, wherein the hollow
space (11) between the outer wall (12) and the inner wall (10) has
an inner height of 3 to 6 mm.
10. The molding tool (1) according to claim 9, wherein the spacers
(13) are columnar and have a diameter of 4 to 6 mm.
11. The molding tool (1) according to claim 10, wherein on the
outside of the outer wall (12) facing away from the hollow space
(11), a steam chamber (15) is formed and communicates with the
through bores (130).
12. The molding tool (1) according to claim 11, wherein the steam
chamber (15) has an inner height (HD) of 2 to 4 mm.
13. The molding tool (1) according to claim 12, wherein the inner
wall (10) has a multiplicity of capillary tubes which extend from
the inner surface facing the molded part to the hollow space
(11).
14. The molding tool (1) according to claim 13, wherein the
capillary tubes have a diameter of 0.1 to 1.0 mm.
15. The molding tool (1) according to claim 14, wherein the molding
tool is produced integrally in one piece out of sintered metal.
16. The molding tool (1) according to claim 1, wherein the spacers
(13) function as flow dividers for the heating/cooling medium (K)
that can be conveyed through the hollow space (11).
17. The molding tool (1) according to claim 1, wherein the inner
and outer walls (10, 12) are oriented approximately parallel to
each other and spaced a constant distance apart from each other and
the spacers (13) extend perpendicular to the inner and outer walls
(10, 12).
18. The molding tool (1) according to claim 1, wherein between
adjacent spacers (13) and the surfaces of the inner and outer walls
(10, 12) facing the hollow space (11), circular through flow
openings (14) are provided for the heating and cooling medium
(K).
19. The molding tool (1) according to claim 1, wherein the through
bores (130) inside the spacers (13) taper conically starting from
the outer wall (12) in a direction of the inner wall (10).
20. The molding tool (1) according to claim 1, wherein the inner
and outer walls (10, 12) each has a wall thickness of 0.3 to 3
mm.
21. The molding tool (1) according to claim 1, wherein the hollow
space (11) between the outer wall (12) and the inner wall (10) has
an inner height of 3 to 6 mm.
22. The molding tool (1) according to claim 1, wherein the spacers
(13) are columnar and have a diameter of 4 to 6 mm.
23. The molding tool (1) according to claim 1, wherein on the
outside of the outer wall (12) facing away from the hollow space
(11), a steam chamber (15) is formed and communicates with the
through bores (130).
24. The molding tool (1) according to claim 1, wherein the inner
wall (10) has a multiplicity of capillary tubes which extend from
the inner surface facing the molded part to the hollow space
(11).
25. The molding tool (1) according to claim 1, wherein the molding
tool is produced integrally in one piece out of sintered metal.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] This invention relates to a molding tool for producing
molded parts from expandable plastic beads. The molding tool has an
inner wall facing the molded part and an outer wall facing away
from the molded part, between which a hollow space is formed for
conveying a heating/cooling medium, and the inner and outer walls
are connected to each other in some areas by spacers.
Discussion of Related Art
[0002] Molding tools of the type mentioned above which are for
producing molded parts from expandable plastic beads, such as
expandable polypropylene (EPP) or expandable polystyrene (EPS), are
known in a wide variety of forms.
[0003] Conventionally, such a molding tool is composed of at least
two molding tool parts, which jointly form a mold cavity in which
the molded body is produced when plastic beads are dispensed into
it, heat is supplied, and the adjacent plastic beads are partially
welded to one another. In this case, a predetermined quantity of
plastic beads is usually introduced into the closed mold cavity
while the mold halves are cooled and then the molding tool parts
and the plastic beads contained in the mold cavity are heated to a
suitable temperature of, for example, approximately 140 to
145.degree. C. through the introduction of large quantities of
steam. Then the tool that has previously been expensively heated is
cooled back down to a temperature of about 60 to 70.degree. C. by
spraying large quantities of cooling water from the back side of
the mold cavity before the molding tool parts are opened and the
molded part can be removed. In this intrinsically established
process, the molding tool is very solidly built, usually of
metallic materials, and on its outside facing away from the mold
cavity, has a generously dimensioned steam chamber in order to
ensure a rapid and sufficient heating of both the molding tool and
the plastic beads inside the mold cavity, which must be completely
penetrated by the steam in order to ensure a homogeneous melting.
Thus, not only are the molding tools that are used expensive, but
also large quantities of steam and cooling water are required,
which results in an extremely disadvantageous energy footprint of
the known devices. In addition, the large quantities of water that
are used place unusual demands on the installation site of such
molding machines.
[0004] There have thus already been a variety of attempts to
optimize molding tools of this type.
[0005] German Patent Reference DE 29 36 273 A1, which defines the
species, discloses a two-part metal mold for producing molded
bodies from pre-foamed plastic granulate, whose metal walls are
embodied as double-shelled and are spaced apart from each other
with spacers, and inside the double shells, hollow spaces are
formed, which can be used to convey a heating/cooling medium
through one molding tool part and in the opposing molding tool
part, can be used to convey steam into the mold cavity. In this
known molding tool, though, it is disadvantageous that the
respective molding tool parts can only be acted on with one medium
at a time, such as the steam is introduced in the region of one
molding tool part, while the temperature control is carried out
with the heating/cooling medium by the other molding tool part so
that the parts that can be produced with molding tools of this kind
can only be embodied as thin-walled because otherwise, neither a
sufficient temperature control nor a sufficient penetration of the
molded part with steam is assured. The known molding tool is thus
only suitable for an extremely limited application range and is not
able to replace the disadvantageous standard molding tool mentioned
above for the production of a wide variety of molded parts.
SUMMARY OF THE INVENTION
[0006] One object of this invention is to avoid disadvantages of
the prior art and to provide a molding tool, which with a
significantly reduced energy consumption and simultaneously
markedly decreased cycle times, permits an efficient, high-quality
manufacture of molded parts from expandable plastic beads.
[0007] In order to attain the above and other objects, this
invention provides embodiments of a molding tool with the features
and other embodiments and modifications of this invention as
described in this specification and in the claims.
[0008] The molding tool proposed by this invention has through
bores inside the spacers, which bores are for conveying steam,
passing through the outer and inner walls, and sealed relative to
the hollow space.
[0009] In this way, it is possible to provide a flow of heating and
cooling medium through the molding tool, namely in the region of
the hollow space between the inner and outer wall in order to
control the temperature thereof and at the same time, to also
convey steam through the through bores in order to control the
temperature of the molding tool and the molded part that is to be
formed inside the molding tool, without the risk of this steam
mixing with the heating and cooling medium. It is thus possible to
produce a molding tool that can be manufactured with significantly
smaller dimensions as compared to the prior art and also both the
heating and cooling medium and the steam can be conveyed through a
corresponding arrangement of through bores to almost all points in
the molding tool and in particular, can also be suitably provided
and applied to critical points of the molded part that is to be
produced, for example, thick and thin points of the material and
the like.
[0010] According to one embodiment of this invention, the spacers
are positioned at regular intervals from one another in the form of
a grid, thus making it possible for a correspondingly large number
of through bores to be provided for conveying steam in the molding
tool.
[0011] Also, particularly when arranged at regular intervals in the
form of a grid, the spacers can also function as flow dividers for
the heating/cooling medium that can be conveyed through the hollow
space so that this medium is favorably and uniformly blended and a
homogeneous temperature distribution is established as well as a
good heat transfer.
[0012] The inner and outer walls can be oriented essentially
parallel to each other and spaced a constant distance apart from
each other. The spacers can extend perpendicular to the inner and
outer walls. This keeps the molding tool according to this
invention very compact.
[0013] According to another embodiment, between adjacent spacers
and the surfaces of the inner and outer walls facing the hollow
space, respective circular through flow openings are provided for
the heating and cooling medium, which in particular makes it
possible to embody or form the spacers as approximately columnar.
They then have a round cross-section, for example.
[0014] It is also possible for the through bores inside the spacers
to taper conically starting from the outer wall in the direction of
the inner wall, making it possible to achieve a longer service life
due to a self-cleaning effect on the side of the mold part cavity.
Also, this measure also achieves a considerable improvement of the
surface quality of the molded part to be manufactured.
[0015] The through bores can, for example, conically taper from an
outer diameter of approximately 1.5 to 2 m n down to 0.3 to 0.5 mm
in the region of the exit to the mold cavity.
[0016] The inner and outer walls of the molding tool according to
this invention can be embodied as very thin, for example, having a
wall thickness of 0.3 to 3 mm.
[0017] The hollow space between the outer and inner walls can also
be embodied as very small, for example with an internal height of 2
to 12 mm, preferably 3 to 6 mm.
[0018] The spacers, which are embodied as columnar according to one
embodiment of this invention, can have a diameter of approximately
4 to 6 mm and can be spaced equidistantly apart from one another in
a grid-like pattern, with adjacent spacers spaced apart from one
another by approximately 5 to 25 mm.
[0019] It is also possible on the outside of the outer wall facing
away from the hollow space to form a steam chamber that
communicates with the through bores, from which the steam can flow
directly into the through bores and from there into the molding
cavity.
[0020] This steam chamber can also be kept very compact and, for
example, can have an inner height of 2 to 4 mm.
[0021] The inner wall of the molding tool according to this
invention can also be embodied or formed with a multitude of
capillary tubes, which extend from the inner surface facing the
molded part to the hollow space. These capillary tubes can have a
diameter of 0.1 to 1.0 mm, for example 0.3 mm. In a molding tool of
this type, it is possible to effectively counteract the filler
formation due to the occurrence of condensate during the production
of molded parts.
[0022] The steaming of the expandable plastic beads that have been
dispensed into the mold cavity inevitably results in a formation of
condensate on the surface of the inner wall facing the subsequent
molded part. According to this invention, this condensate is drawn
into the capillary tubes by capillary action. As soon as the
steaming causes the molded part to form, the molded part expands
against the surface of the inner wall and displaces the condensate
further into the capillary tubes, from where the condensate travels
into the hollow space and into the heating and cooling medium that
is then conveyed through the hollow space. Conversely, though, the
heating and cooling medium, as it passes through the hollow space,
cannot pass through the capillary tubes into the mold cavity
because the expanded molded part closes the capillary tubes in the
mold cavity in a sealed fashion.
[0023] According to another embodiment of this invention, a molding
tool according to this invention can particularly be integrally
manufactured out of sintered metal so that the low wall thicknesses
and specific geometries can be manufactured in a simple way as
explained above. In particular, selective laser sintering (SLS) can
be used to produce such molding tools according to this invention
with through bores extending through spacers embodied or formed in
the form of columns in integral in one operation from suitable
materials. In particular, suitable metal powders are used for this
purpose.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Other embodiments and details of this invention are
explained in greater detail in view of exemplary embodiments shown
in the drawings, wherein:
[0025] FIG. 1 shows a stepped section taken through a molding tool
according to this invention; and
[0026] FIG. 2 shows the section taken through the molding tool
according to FIG. 1, in an enlarged view from a different
angle.
DETAILED DESCRIPTION OF THE INVENTION
[0027] FIGS. 1 and 2 show an exemplary embodiment of a molding tool
according to this invention or more precisely stated, of a molding
tool part thereof, which in cooperation with another molding tool
part that is not shown here, but that is in principle constructed
in a similar way, delimits a mold cavity in which a molded part can
be produced from expandable plastic beads in an intrinsically known
way.
[0028] The molding tool part, also referred to simply as the
molding tool or the mold, is identified as a whole with the
reference numeral 1 and includes an inner wall 10 facing the molded
part and the mold cavity and an outer wall 12 facing away from the
molded part and these walls are positioned spaced apart from each
other by spacers 13 embodied or formed in the form of columns so
that between the spacers 13, a continuous hollow space 11 is
formed.
[0029] The spacers 13 are provided at regular intervals,
particularly in a grid-like arrangement. For example, they are
arranged in lines that are labeled L1 and L2 in FIG. 1. The
individual spacers of a line L1 are arranged so that on the
adjacent line L2, the spacers are each positioned offset by
one-half the spacing distance. All of the lines L1, L2 extend
parallel to one another. The distance between adjacent spacers is
approximately 5-25 mm.
[0030] The columnar embodiment of the spacers, which have a
diameter of 4 to 6 mm for example, leaves room between the surfaces
of the inner wall 10 and outer wall 12 facing the hollow space 11
and the respective spacers 13 for a circular through flow opening
14. It is thus possible, inside the hollow space 11, to allow a
heating and cooling medium indicated with the arrow K in FIG. 2 to
circulate in order to heat or cool the surfaces of the molding tool
to the desired temperatures before, during, and after production of
the molded part. The heating and cooling medium circulates around
the spacers 13 arranged regularly in a grid and they serve as flow
dividers so that a homogeneous distribution and good circulation of
the heating and cooling medium K is achieved. The connections for
the heating/cooling medium are not shown but can be provided at a
suitable point.
[0031] This embodiment makes it possible to provide the depicted
molding tool with a cooling that closely follows its contours when,
after completion of the foaming step, a cooling medium such as
water is conveyed through the hollow space. In this way, in
comparison to known methods that are based on spray drying, a
significant reduction in cooling water consumption can be achieved
and there is no longer coolant escape of any consequence from a
molding machine that is equipped with the molding tool according to
this invention, so that a virtually dry operation is achieved. This
makes it possible to achieve a reduction in cooling water
consumption of up to 75%.
[0032] Also, a through bore 130 is formed inside each columnar
spacer 13 and the through bores pass through the inner and outer
walls 10, 12 of the molding tool 1. The through bores, starting
from the outer surface 12 and the inlet opening 130a there, taper
conically in the direction of the inner surface and the outlet
opening 130b there, for example, from a starting diameter of
approximately 1.5 to 2 mm down to 0.3 to 0.5 mm.
[0033] It is thus possible, through each of the individual spacers
13 in the region of or near the through bore 130 embodied therein,
to convey steam D from the outer wall 12 in the direction of the
inner wall 10 and from there, into the mold cavity so that the
expandable plastic beads, which have been dispensed into the mold
cavity in an intrinsically known way, can be steamed with hot steam
and melted to form the molded part.
[0034] The steam chamber 15 provided for the steam treatment is
implemented by a wall 150 that is mounted onto and spaced a certain
distance apart from the outer wall 12, where the inner height HD of
the steam chamber is for example 2 to 4 mm. Here, too, for the sake
of simplicity, connections and supply lines to the steam chamber 15
are not shown.
[0035] The embodiment of through bores 130 inside the spacers 13
ensures that the coolant circulating in the hollow space 11 is
completely separated from the steam D conveyed through the through
bores 130 and no mixing of the two occurs, which also makes it
possible to considerably reduce steam consumption as compared to
known methods. A steam reduction in comparison to conventional
methods on the order of 65% is possible.
[0036] The above-explained conical tapering of the through bores
130 for the passage of steam also significantly improves the
surface of the resulting molded parts and increases the service
life of such a molding tool 1 because a self-cleaning effect occurs
and the molded part compound is effectively prevented from
penetrating into the through bores 130 for the steam. Furthermore,
the grid-like arrangement of the through bores 130 inside the
regularly spaced spacers and the flow of cooling medium distributed
across the entire area of the molding tool 1 enables temperature
control and steaming that are effective and largely independent of
the geometry of the molded part that is to be produced. Naturally,
depending on the requirements, in certain regions of the molding
tool, a higher or lower number of spacers 13 and through bores 130
embodied therein can be provided for passage of the steam D.
[0037] In particular, despite the complex geometry of the molding
tool 1 shown in the drawings, it can be produced integrally in one
piece and in a single operation from a suitable metallic material
by using the so-called laser sintering method and the molding tool
mass can be reduced through a significant reduction in the required
wall thicknesses. The inner and outer walls 10, 12 can be produced
with wall thicknesses of 0.3 to 3 mm, for example. In any case, the
large number of spacers 130 provided ensures a high stability of
the inner and outer walls 10, 12 adjoining the hollow space. The
tool weight of such a molding tool can thus be considerably reduced
as compared to the conventional method. In this case, weight
reductions of up to 70% are possible.
[0038] Through such a weight reduction, it is also possible for the
entire machine that accommodates the molding tool to be of a
significantly smaller design because the masses to be moved are
also considerably reduced.
[0039] Also, the required process time for molding a molded part is
also significantly reduced by this particularly compact embodiment
of a molding tool because the heating and cooling times are
considerably reduced in accordance with the achievable mass
reduction in the molding tool and the achievable steaming and
cooling. Processing time reductions of more than 40% as compared to
conventional manufacturing processes have been achieved.
[0040] In order to carry off any condensate forming in the mold
cavity, particularly on the surface of the inner wall 10, it is
also possible to provide capillary tubes, not shown here, with an
average diameter of such as 0.1 to 1.0 mm, preferably 0.3 mm, in
the inner wall 10 in a sufficient, for example, regular
arrangement, which extend into the hollow space 11 and by which
condensate can be carried off into the hollow space 11. This
effectively prevents a filler formation on the surface of the
molded part.
[0041] The molding tool according to this invention is particularly
suitable for producing molded parts from expandable plastic beads,
but this invention is not limited and this principle can also be
used with other suitable molded part manufacturing processes. It is
also possible to use other manufacturing processes in addition to
the above-mentioned laser sintering to produce the molding tool
according to this invention.
* * * * *